To compare the anti-leukemia efficacy, acture toxicity and biochemical pharmacology of E. coli, Erwinia, adn PEG-modified E. coli ASP at the Investigational window in all patients. L-asparaginase has become a vital componet in the treatment of children with acute lymphoblastic leukemia. The antileukemic activity of ASNase is thought to result from depletion of serum asparagine.